The project is concerned with the development of the nervous system using tissue culture technique: 1. Study of survival and development of architectonic patterns in the hypothalamic region. The nuclear groups of the mamillary configuration and infundibular nucleus survive in culture for at least 50 days. Both regions display different developmental patterns. 2. Study of axonal growth patterns in the mamillary configuration in isolation. Despite the loss of their entire extramamillary inflow and the absence of the normal target region, the mamillary tracts remain preserved and new growth sprouts at the point of the axonal transsection. 3. Study of the developmental patterns in the Organ of Corti of the newborn mouse. The organization of the neuronal structures may be similar, even in minor details, to that of the intact animal. The differentiation of the supporting elements occurs during the first two weeks. The nerve fibers which lose their synaptic connections with the hair cells regain the capacity to grow. 4. Relationships between the growing nerve tip and its leading glial cell. A time-lapse study showing an interaction of these two elements during the early phase of neuronal growth.